This invention relates to a valve having special utility for controlling flow of coolant gas (air) to or through the blades of high speed turbines, especially turbine wheels used in hot gas turbine engines.
The turbine blades (wheels) in hot turbine engines customarily operate at relatively high temperatures, e.g., about 2,000.degree. F. The service life (structural integrity) of such turbine wheels can be preserved/extended by passing a coolant gas (air) through passages in the blades. Cooling the turbine blades also tends to maintain small clearances between the blade tips and the passage surfaces, thereby improving turbine efficiency.
Under the present invention, it is proposed to provide a valve structure that can be used to supply a variable frequency pulsed flow of coolant air to the turbine blade system; presently preferred pulse frequency range is from steady state flow (no pulses) to 725 on-off pulse cycles per second. The valve will be designed to handle high pressure air at about 200 p.s.i.g., at temperatures up to about 900.degree. F. The valve flow passage will be a circular straight-through passage offering minimum obstruction to fluid flow.
The purpose in providing a pulsing flow, as opposed to a steady constant flow, is to artificially generate scrubbing turbulence on the blade surfaces (passages) and thereby improve the heat transfer efficiency.
The principal object of the invention is to provide a pulsation valve that can be incorporated into an existing turbine engine at minimum expense. The valve is designed to be manufacturable at relatively low cost, using as many standard shelf components as possible. The valve is designed to serve as a test mechanism for investigating the effect that varying the pulsation frequency has on blade cooling efficiency.